On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior

Abstract

On-surface synthesis is an emerging approach to obtain, in asingle step,precisely defined chemical species that cannot be obtained by other synthetic routes.The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices.A facile on-surface chemistry route has now been used to synthesize the strong electron-acceptor organic molecule quinoneazine directly on aC u(110) surface,v ia thermally activated covalent coupling of para-aminophenol precursors. The mechanism is described using ac ombination of in situ surface characterization techniques and theoretical methods. Owing to astrong surface-molecule interaction, the quinoneazine molecule accommodates 1.2 electrons at its carbonyl ends, inducing an intramolecular charge redistribution and leading to partial conjugation of the rings,conferring azo-character at the nitrogen sites.Organicheterostructuresbasedonelectronacceptor-donor organic molecules on surfaces have become strategic materials owing to their huge technological impact in fields such as organic light-emitting diodes (OLEDs), organic field effect transistors (OFETs), or solar cell devices,amongst others.In electronic devices,o rganic layers are placed on metallic surfaces for electrical contact, and the structure of the metalorganic interface enormously affects the performance.[1] In particular,s ome molecules promote charge transfer at the interface with metal electrodes owing to their donor (acceptor) nature,which may induce energy level realignment that can be exploited to tune the transport properties of the system. [1][2][3][4][5] Despite the potential impact of this approach, only af ew molecules have been shown to efficiently donate (or accept) significant charge,t his quality being related to the presence of donor (acceptor) moieties in their structures.[6] A typical example is tetracyano-p-quinodimethane (TCNQ), as trong acceptor molecule that when deposited on Cu(100) accommodates around 1.6 electrons whereby almost one electron aromatizes the central hexagonal ring and the remaining fraction of the charge is accommodated in one of the peripheral nitrogen atoms of the cyano groups.[3]On the other hand, on-surface synthesis can generate unique molecules or extended molecular architectures that have been rationally formed via alternative synthetic routes to those available through solution-based chemistry. [7,8] These surface-stabilized species can lead to compounds that are difficult or impossible to obtain via conventional synthetic procedures. [9][10][11][12] Herein, we combine both of the aforementioned features. We show that the on-surface coupling reaction of two simple and inexpensive para-aminophenol (p-Ap) molecules can be employed to form aq uinonoid-like derivative,q uinoneazine (QAz). This molecule has been theoretically proposed for organic electrodes owing to their extreme redox voltages,and it can also be employed as an intermediate in the preparation of several chemically and biologically active ...

Copper-assisted oxidation of catechols into quinone derivatives

“…These values are large, already exceeding those obtained with the best molecular electron acceptors. 28,45 In core level spectra, the increased electronic density around the probed atoms, corresponding to the larger electron donation from the substrate (from half-dehydrogenated to fully-dehydrogenated HHTP), is consistent with the global shift to lower binding energies, −0.2 eV for C 1s core level spectra, and −0.4 eV for the ketone contribution to the O 1s core level spectra. In the case of the semiquinone, charge accumulation is found below and on top of the central C ring, which is closer to the surface (see Fig.…”

Boosting Rechargeable Batteries R&D by Multiscale Modeling: Myth or Reality?

“…159 Similar approaches were exploited in order to account for the incidence on redox potential of isomerism/N substitution in pentalenedione derivatives 160 and for deciphering the ranking of naphtho-, biphenyl-, and biphenylenequinone isomers. 161 Research area on redox-active compounds bearing azo groups seems indeed to be promising thanks to recent investigations having demonstrated that quinoneazine can accommodate 1.2 electrons at its carbonyl ends when grafted to Cu(110), 162 whereas azobenzene-4,4-dicarboxylic acid lithium salt (ADALS) can correspond to a highly reversible electrode material for alkali-ion batteries, 163 with charge/discharge plateaus at 1.50 and 1.55 V vs Li + /Li, respectively. Additional insight on the structure−property relationship may also be gained through the consideration of plots of electrostatic potential on the molecular surface.…”

Role of the Structure and Reactivity of Cu and Ag Surfaces in the Formation of a 2D Metal–Hexahydroxytriphenylene Network

“…Starting from alcohols, such oxidation (or dehydrogenation reaction) is straightforward on copper surfaces − but also partially occurs on silver ,− and gold surfaces . A peculiar kind of alcohol, the hexahydroxytriphenylene (HHTP) molecule, has attracted much attention in this respect.…”